1. Field of the Invention
The present invention relates generally to a disk drive for magnetically recording data on a disk medium and more particularly to a method and apparatus for write control under a changing-temperature environment.
2. Description of the Related Art
Generally, a disk drive in a magnetic disk apparatus, a magneto-optical disk apparatus or the like is so configured to magnetically record data on a disk medium (hereinafter referred to as disk) and restore magnetic recorded data on the disk to its original form.
The disk drive has been utilized as not only a storage device of a personal computer, as conventionally, but also as a data storage device of a digital TV or various kinds of digital equipment incorporated in a vehicle, its application field being expanded. For this reason, particularly as an operating environment of the disk drive, an appropriate measure for controlling the temperature environment has been demanded.
Usually, to secure a specific reliability, a temperature range which allows the disk drive to operate normally is set up as a product specification preliminarily. For the disk drive, write operation for magnetically recording data on a disk and read operation for reading data from the disk are prominent specifications.
Usually, in the disk drive, the read operation has a wider tolerable range which allows itself to operate against a temperature change than the write operation. Contrary to this, for the write operation, its tolerable range is set relatively smaller under high temperature environment compared to a specified temperature in order to secure reliability of data recorded on a disk.
On this background, there has been proposed a technology which monitors temperatures inside the drive with a temperature sensor and if a change in low temperature exceeding its tolerable range occurs, prohibits the write operation (see Jpn. Pat. Appln. KOKAI Publication No. 7-6560). Further, a technology in which an alarm is dispatched to a system or the operation of a disk drive is stopped, for example, under high temperatures has been proposed (see U.S. Pat. No. 5,115,225).
Generally, the disk drive executes write operation for writing user data into a specified position on a disk according to a write command (data write instruction) from a host system (personal computer or digital machine).
On the other hand, the disk drive has a write operating mode which the host system does not concern (not concerned with issue of the write command) as well as the write operation for recording ordinary user data as described above.
More specifically, a write operating mode called re-assignment processing is available at the time of ordinary read operation or write operation. This processing is an alternative processing for specifying a region on a disk in which data cannot be recorded so as to change the region to another alternative region.
For example, if a read error occurs during read operation, error correction/repair processing is executed by an error detection/correction (ECC) function. In this case, right data after error correction is moved to another position different from the recording position on the disk in the disk drive. The recording position used up to then is prohibited from being used thereafter.
This processing is simply a called re-assignment processing or because it is carried out at the time of read operation, particularly, it is called read reassignment processing. Regardless of the fact that only a read command is issued from the host system at this time, data is automatically written into a certain region on the disk. In the re-assignment processing, write operation for updating address management table information such as a file allocation table recorded in a predetermined position (for example, most outer peripheral track) on the disk is executed.
The write reassignment processing may be executed at the time of write operation also. Generally, in the disk drive, upon read/write operation, a head positioning operation (servo control) of positioning the head at an object track (recording region of access object) on the disk is executed. Upon write operation, the head positioning accuracy is verified to heighten the reliability of data recording and only when a sufficient positioning accuracy is verified, data write is executed.
At the time of this head positioning operation, write retry operation is repeated within predetermined times until a sufficient positioning accuracy is obtained. If the sufficient positioning accuracy is obtained, write operation upon the object track on the disk is executed. On the other hand, when the sufficient positioning accuracy cannot be obtained even if the predetermined retry times are exceeded, a write position on the disk (for example, a sector in the object track) is automatically changed to a certain region (sector) on the disk and the data write is carried out. This processing is an alternative processing called write reassignment processing. In this write reassignment processing also, a write operation mode in which address management table information accompanied by the re-assignment processing is automatically updated, is executed separately from the write operation corresponding to a write command from the host system.
Further, the disk drive has a function of recording disk usage history, for example, history information such as power-on frequency at a specific position on the disk. This function is automatically started when the disk drive is powered on. This function executes updating of the history information at an empty time just after the power is turned ON or during the operation regardless of a command from the host system. In this case, data is automatically written into a certain region on the disk regardless of the fact that no write command is issued from the host system.
As described above, in the disk drive, the write operation mode of recording data other than ordinary user data on the disk is automatically executed regardless of the write command from the host system. When the write operation mode is executed, it can be thought that the temperature environment within the disk drive becomes a high temperature condition exceeding a specified value. The host system cannot control write operation because the host system is not engaged in the write operation even though the reliability of data to be written into the disk is degraded due to a high temperature. In the worst case, address management table information accompanied by the reassignment processing is lost, thereby possibly disabling reading of recorded data from the disk.